Case Example: -introduction -material and methods -results Case Exam ple I I -sensitivity analysis -costs of lameness Sim herd: -effect of treatments -discussion Advanced Herd Managem ent -representative Jehan Ettem a -usable in practice -other applications Economic decision making on prevention and control of clinical lameness in Danish dairy herds Material and methods Introduction SimHerd III (Østergaard et al. 2003) Harris et al. (1988) DKK 195 Whitaker et al. (1983) DKK 500 Enting et al. (1997) DKK 775 -stochastic McCluggage et al. (1985) DKK 1574 -dynamic Kossaibati et al. (1997) DKK 2931 -mechanistic Parameterisation: definition of the State of Nature Common strategy of working with Simherd ”complete set of model input parameters” 1. Formulate treatments, strategies and scenarios: ”what if...” 2. Parameterisering: risk factors, effects, design of your farm General production and management system of modern -literature study Danish dairy herd -field study -both emperical and normative knowledge Biological variables 5% Mortality 3. Programming, if necessary (new disease) Reproduction strategy 14 mo. Start breeding heifers 4. Validation: sensitivity analysis Replacement strategy 427 Max days open 5. Run of the actual simulations Drying-off strategy 5,0 Liter Yield at drying off 6. Analize and interpret the results Prices DKK 2,20 Milk price 1
Parameterisation specific for lameness Parameterisation: definition of the State of Nature Risk factors, effect parameters, interrelations Modern Danish dairy herd Difficulties with respect to lameness: •Herdsize: 120 cows � Lameness is a symptom of several diseases: •Milk yield level: 8500 kg ECM � Digital dermatitis 25% of the lameness causes � Sole Ulcer •2 kinds of roughage and concentrates 21% � White line disease 17% •Minimum length dry period: 49 days � Interdigital Hyperplasia 7% •Involuntary culling: 18-20% � Sole bruising 8% •Stillbirths: 11% (1. parity) and 6% (older) � ... •Heat detection efficiency: 50% Parameters: result of weighted average of values •Feeding of milk replacer found in literature for dermatitis, sole ulcer... •Common incidence of diseases (e.g. mastitis 25%, DA 1.4%) Cow specific risk: logistic regression model Risk factor logit value Base risk 0,16 -base risk 0,16 -1,66 Risk of lameness in the third lactation for a herd-average -parity 2 OR 0,78 -0,25 producing cow without previous cases of any disease -milk yield potential + 1 kg OR 1,08 0,08 -december (high risk) OR 1,84 0,61 Cow specific risk factors Parity 1 vs. 3, OR 0,56 1 Parity 2 vs. 3, OR 0,78 P(123) = ------------------------------ Parity 4 vs. 3, OR 1,25 1+e -( β 0 + β partiy + β milk yield + β season ) Milk yield potential, OR per kg 1,08 Lactational recurrence, OR 2,31 1 High risk season, day Sept-May P(123) = ------------------------------ = 0,22 High risk season vs. Remaining year, OR 1,840 1+e -(-1,66 + -0,25 + 0,08 + 0,61 ) Lactation stage, time of occurence Cow specific risk: logistic regression model Triggering of the occurence of lameness Incidence Draw a sample from a uniform distribution around P = 0,22 25 X = cow becomes lame 20 15 10 5 1 2 3 4 5 6 7 8 9 10 11 12 1 months of lactation P(123) = ------------------------------ = 0,22 Gamma distribution (2,60) ( α , β ) 1+e -(-1,66 + -0,25 + 0,08 + 0,61 ) 2
Effect parameters Effect parameters Milk yield, feed intake, body weight Reduced milk yield 0,937 40 640 Duration in days 147 35 620 30 Kg ECM and SFU milk yield Kg Body Weigth Daily weight loss, ratio of current weight 0,110 25 600 Duration in days 35 20 580 feed intake 15 560 Reduced feed intake, ratio 0,960 10 body weight 540 Duration in days 35 5 0 520 1 5 9 13 17 21 25 29 33 37 41 Reduced conception rate, OR 0,78 weeks after calving Duration in days 147 SimCow: simulation of the production of an individual cow as a function of a certain production strategy Euthanised or died, ratio of lame cows 0,035 -mimic interaction between milk loss, feed intake and bodyweigth Effect parameters Design of ”what if” scenarios Treatment costs -preventive measures, management strategies � Preventive trimming Each case of lameness is treated 1.4 times In 80% of the cases the trimmer/veterinarian treats the cows � Footbaths � Increase the access to pasture Kossaibati and Esslemont 1997 � Rubber covering of concrete floors -interdigital lameness: 332 DKK � ...imagination -sole ulcer: 700 DKK Zeddies et al. 1997 Recurring difficulty with respect to lameness: Mild case: 223 DKK Efficacy of measures only for certain diseases Severe case: 543 DKK footbaths � infectious diseases rubber floors � trauma related diseases This study: 400 DKK per lameness cases (treated 1.4 times) Simulation procedure Design of ”what if” scenarios Reduction of the base risk in a herd -simulation over 10 years � Preventive trimming OR 0,66 evaluation of long term effects � Footbaths OR 0,9 � Increase the access to pasture + 2 months -500 replications � Rubber covering of concrete floors OR 0,66 stochastic Base risk in a herd that trims cows twice a year vs. once: 0,16 x 0,6 = 0,10 -discard the first 5 years ”what if” in different herds: ”burn in” period -”what if” milk yield level of the herd is higher? -”what if” conception rate is low in the herd? -results are the average of the last 5 years 3
Technical comparison of two herds: Results high base risk (0,16) vs. low base risk (0,08) of lameness Result BR 0,16 BR 0,08 Diff. Comparison of a low and high risk herd Cases of lameness 28.97 14.84 -14.13 * Cow year 118.42 118.42 0.0 External validation: sensitivity analysis Milk/cow, ECM 8493.5 8531.5 +38.0 * Effect of milk quota Feed/cow, SFU 5599.7 5610.3 +10.6 * Replacement rate 43.36 43.04 -0.32 * Effect of different (re)production levels in a herd Dead cows, % 3.87 3.43 -0.44 * Efficacy of preventive measures * Significant difference: p < 0.05 Economic comparison of two herds: Economic comparison of two herds: high base risk (0,16) vs. low base risk (0,08) high base risk (0,16) vs. low base risk (0,08) Result BR 0,16 BR 0,08 Diff. Attribute costs to lameness: Sale: Milk 2112.7 2122.8 +10.2 * -Difference in milk sale is DKK 10.200 x 1000 DKK Heifers 53.3 56.6 +3.4 * -result of 14 cows less lame in ”low risk herd” Total 2359.4 2372.5 +13.0 * -10.200/14 = DKK 730 milk loss per lame cow Purchase: Feed, cows 838.2 840.2 +2.0 * x 1000 DKK Other costs 116.6 107.9 -8.7 * -”low risk herd” has lower replacement rate Total 1242.9 1235.8 -7.1 * -on average the cows are older -average production per cow is higher (indirect effect of lower lameness inc.) Margin: Total x1000 DKK 1116.5 1136.6 +20.1 * Per cow 9429 9594 +165 * Per kg ECM 1.110 1.124 +0.015 * Economic comparison of two herds: External validation of the model: high base risk (0,16) vs. low base risk (0,08) Sensitivity of model to the input parameters How sensitive is the outcome of the model to the setting of the input parameters Attribute costs to lameness: Costs of premature culling -reduced milk yield (RMY): 8,6%, based on literature studies -Loss of future income -lowest value in literature: 5,2% -Reduced sale of heifers -highest value in literature: 12% -Costs of raising replacement Comparison of two herds (base risk 16% and 8%): Attribute costs to lameness: Reproduction With RMY of 12%: 202 DKK +23% -Extra insemination With RMY of 8,6%: 165 DKK -Days open With RMY of 5,2%: 158 DKK -4% -Calves per cow Model is most sensitive to the setting of ”reduced milk yield” 4
External validation of the model: Economic comparison of two herds: Sensitivity of model to the input parameters Costs per case of lameness: DKK 1430 Situation without milk quota: Herd with high incidence of lameness: 1,006,035 Herd with low incidence of lameness: 1,010,870 +4800 Situation with milk quota: correct for amount of milk produced Costs per case of lameness: DKK 1036 Low incidence herd produces the same amount of milk, with fewer cows Why simulation without quota? Buying and selling quota interferes heavily with the economic results Costs per case of lameness in different herds Economic comparison of two herds: Lower milk yield potential DKK 1322: lowest Costs per case of lameness: DKK 1430 -margins are lower, in general Lower pregnancy chance DKK 2065: highest ”what if” ...the compared herds differ -difference in margin devided by fewer cases of lameness -increased days open > longer lactations > cows spend more time in ”tail of the lactation curve” (low risk): fewer cases! Milk yield potential is 30 kg vs. 34 kg ECM DKK 1322 Milk yield potential is 38 kg DKK 1455 25 Pregnancy chance is 40% vs. 50% DKK 2065 20 Heat detection eff. is 40% vs. 50% DKK 1661 15 10 5 1 2 3 4 5 6 7 8 9 10 11 12 months of lactation Economic comparison preventive measures: Economic comparison preventive measures: Difference between grazing and zero-grazing farms Difference with the ’no prevention’ strategy in zero-grazing farms Zero grazing Grazing Per cow year* Lame cows* 33.3 -4.2 No prevention Rubber floor or trim twice Footbath Per cow year* Margin* 9,377 +51 Lame cows* 33.3 -10.9 3.7 Total margin 1,110,438 +6,075 Margin* 9,377 +126 +44 Total margin 1,110,438 +14,781 +5,257 •other aspects of grazing interfere with the results. •Feeding of roughage vs. grazing •Labour •Other benificial effects on health •... 5
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